jar-dependencies must explicitly depend upon ruby-maven #97

jar-dependencies currently uses ruby-maven to fetch and activate jars, but it does not specify ruby-maven as a dependency.

That disconnect triggers errors during the jar-dependencies post-install hook if ruby-maven is being installed in parallel. I have reported that issue to bundler here: ruby/rubygems#9386

Bundler/RubyGems should not be allowing in-progress gems to be activated or seen by post-install hooks, but by making jar-dependencies explicitly depend upon ruby-maven we can avoid the issue; bundler will ensure that ruby-maven has completed installing before the jar-dependencies hooks are run.

I pushed a test of this to the stringio repository, using a prerelease 0.5.6.pre1 of jar-dependencies. It appears to eliminate the CI failures caused by the partial gem activation issue: ruby/stringio#209